In general, substrate materials used for the growth of nanomaterials are limited to brittle and flat insulating oxide materials, such as alumina (Al2O3) or silica (SiO2). It is required that such substrates are stable at an adequately high temperature needed for the growth of nanomaterials; have mechanical compliance and flexibility so that they are transferred to a broad array in a basic structure (flexible polymer, non-planar structure); enable rapid and large-scale production of complicated device structures; and realize ohmic electrical contacts in all contacts in the case of electrically conductive materials, and have a work function similar to the work function of nanostructures so that electric power is used efficiently.
Herein, thin films may satisfy all of the above-described four requirements or at least three of them, when they are composed of nano-size platelets stacked successively and electrically insulating substrates are required. Transparent and electrically insulating thin films are also included in such thin films. Other examples for use in conductive plates include layered nanoclay (vermiculite, mica, montmorillonite, etc.) plates or layered hexagonal boron nitride (HBN) plates, and layered graphene-based plates having mechanical compliance.
Graphene means one layer of carbon with a hexagonal structure, and is a two-dimensional carbon structure having a thickness corresponding to one atom. In general, it is known that graphene is made of graphite found in pencils and has excellent physical properties as compared to carbon nanotubes.
Since nanomaterials, such as nanotubes, and graphene exhibit excellent conductivity and mechanical properties, have a large surface area and are very stable under non-oxidizing environment, they are useful as constituents forming nanoelectric devices including flexible devices. Therefore, there has been a need for developing hybrid technology to obtain a synergic effect by combining such excellent properties of the nanomaterials and graphene.
The inventors of the present invention have found that three-dimensional structures obtained by depositing a metallic catalyst array onto a graphene film and growing nanomaterials via a plasma enhanced chemical vapor deposition (PECVD) process, etc., have excellent conductivity and mechanical properties, such as flexibility and elasticity. The present invention is based on this finding.